How My Day Started with a Cold Shower Surprise
Okay folks, buckle up. This morning I jumped in the shower ready to conquer the day, and BAM, felt like I was hit by an iceberg. My Rinnai tankless water heater decided it was time for an Arctic expedition. My wife was yelling from the kitchen sink about the same icy trickle. Not exactly the relaxing start I pictured.
Right then, I knew I had to dig into this machine mounted on my garage wall. I grabbed my phone first, figuring there must be some fancy remote app thing. Tapped it open, swiped around… nada. Couldn’t find any temperature settings at all. Just usage stats staring back at me. Felt like a wild goose chase on a tiny screen. So much for tech making life easier.

Face-to-Face with the Metal Box
Abandoned the phone idea. Marched myself out to the garage, stood staring at this sleek metal box humming away. It looked straightforward enough, right? Found the control panel. Saw two buttons near the display: a little one pointing down, another one pointing up. Below that, a button with a flame symbol on it – seemed promising. Poked the ‘Up’ button. Nothing happened. Poked it again, maybe harder than necessary. Still nothing. Started cussing under my breath. My temper was flaring hotter than the stupid heater.
The Lightbulb Moment (Almost Literally)
I’m standing there, probably looking ridiculous, when I remember the flame button. Figured what the heck, might as well try holding that down while messing with the arrows. Pressed and held the flame button. Then I jabbed the ‘Up’ arrow. Eureka! The display changed! Instead of just showing the current water temperature, it suddenly flashed what looked like a set point number. My kid ran by yelling about the football game starting, distracting me, but I stayed focused (sorta). Held the flame button, mashed the ‘Up’ arrow some more. Watched the number creep up from its Antarctic setting of 105°F. Bumped it up to 120°F. Felt pretty proud of myself, like I’d cracked a secret code.
So here’s the quick and dirty steps I figured out:
- Hunt down the physical control panel on your actual Rinnai unit.
- Hold down the button with the flame symbol on it.
- Smash the ‘Up’ arrow button to raise the temperature while holding the flame button. See the number change on the screen.
- Release both buttons when you hit your magic number (I liked 120).

That’s it. Done. Saved myself future hypothermia.
Aftermath & Why It Feels Stupid
After setting it, I ran back inside like my pants were on fire to test the kitchen sink. Turned on the hot tap. It took a bit for the heater to wake up and get the water flowing hot – yeah, that lag is annoying but normal for these things, I guess. Then, glorious hot water! Victory felt sweet.
Honestly though? This whole thing shouldn’t be this dumb. Why hide basic settings behind a button combo you need instructions for? Why can’t the stupid app just let you do it? Feels like they make it slightly awkward on purpose, maybe so you call a pro? I don’t know, but it got me grumbling again. Saved myself a service call fee though, which was the whole point. Who can afford those these days? Now I just gotta make sure the kids don’t find the buttons and crank it to volcano levels. Fingers crossed.